1. Field of the Invention
This invention is related to the field of computer system backup/restore software.
2. Description of the Related Art
Various software tools existing for backing up computer systems and restoring backup data to computer systems. Such tools are provided to permit recovery, at least to the most recent backup state, from user error, hardware failure in the backed-up computer system, or other disaster situations originating outside the computer system that cause data loss such as by damaging the computer system. User error may include activities such as accidental file deletion, file corruption, or erroneous file content change.
In some cases, such as certain user errors, only the affected files need be restored to the computer system. In other cases, such as hardware failure or other disaster, the entire backup state is restored to the computer system after the failure is corrected. The failure may be corrected by replacing the faulty hardware in the same computer system. In other cases, the entire computer system may be replaced. The computer system may be replaced because the faulty hardware cannot be replaced or repaired, or because it is more cost-effective to purchase a new computer system than to attempt repair of the failing computer system.
Whether hardware is replaced or the entire computer system is replaced, in some cases it is not possible to provide the same disk configuration. Over time, the readily-available fixed disk drives (or “hard” disk drives) change. For example, the capacity (or “size”) of the disk drives tends to increase over time. Thus, if disk drives are being replaced in a computer system, it is likely that higher capacity disk drives will be used as compared to those being replaced. If a new computer system is being deployed, the new computer system will probably include higher capacity disk drives than the computer system being replaced. Particularly, it is common to have fewer drives of higher capacity.
When the disk configuration (i.e., number and capacity of disk drives) is not the same between a backed-up computer system (that is, a computer system from which a backup was made) and the restore computer system (that is, the computer system to which the backup is being restored), restoration of the backup is problematic. For example, if the number of disk drives is the same between the configurations, but the new configuration has more total capacity, then space may be wasted on the new configuration due to some of the space being unallocated.
Furthermore, the storage in the original disk configuration is typically divided into various volumes onto which filesystems are mapped. Volumes may be mapped to a single disk drive or multiple disk drives. Multiple disk drives may be combined into a volume as a single logical storage. In other cases, a volume may have protection/performance attributes such as mirroring, redundant array of inexpensive disks (RAID) configurations, or striping. Such performance/protection attributes are implemented by mapping the volume to multiple disk drives. Furthermore, various filesystems may have various sizes based on the original disk configuration. If the disk configuration in the restore computer system differs from the original disk configuration, how to map volumes and filesystems to the new disk configuration may not be immediately apparent.
Some restoration tools will permit the new disk drives to be higher capacity in the restore computer system as long as the same number of disk drives are included. Such tools, during the restoration, expand the size of volumes on a given disk drive in proportion to the size difference. However, such tools are limited to use when the same number of disks are provided and are limited in flexibility. Other tools, such as the VERITAS Bare Metal Restore™ (BMR) product (version 4.5) available from VERITAS Software Corporation (Mountain View, Calif.) permit the user to map the volumes to a new configuration or exclude volumes from a restore, but do not permit the volume attributes to be changed. Still other tools (such as the Intelligent Disaster Recovery Option™ (IDR) of the VERITAS Backup Exec™ product available from VERITAS Software Corporation for the Windows platform) create the volumes on the restore system, then launch Microsoft's disk administration utility to permit changing various volume attributes (except for the system partition that includes the operating system software). These tools are also limited since the system partition cannot be modified. Additionally, these tools are limited in that the volume must be created on the restore computer system before it can be modified. Some volumes may not be successfully created. For example, volumes that are mapped to more than one disk drive may not be successfully created if only one disk drive is included in the restore system (e.g. striped or mirrored volumes). Finally, an administrator may manually create volumes and restore data manually. However, such a mechanism may be time consuming (both for the administrator and any users awaiting the restore) and may increase the likelihood of error.